51813_Sturgeon biodioversity an.PDF

iningstomachs of copperfish,Coreius heterodom,
for the presence of sturgeon eggs (Deng & Xu 1991).
Hydrologicaldatawere provided bylocalmonitor-
ing stations.Catchesweredetermined fromour
census or bylocal fisheries managers. All datawere
analyzedusing SAS and MSA (Beijing University
1993)software.

reachto the mouth(Figure 1). It alsooccurs in the

WusulijiangRiver(alsoknown as the Ussuri Riv-

er), atributary to theAmurRiver, but it is now se-

verelydepleted in theSonghuajiangRiver(also

known as the SungariRiver). Thespecies consists

of a few distinctpopulations. Ingeneral,there is a

gradient ofincreasingmeantotallength(TL) and

bodyweight(BW) ofspawningstocksfrom the up-

per to the lowermiddle reaches(Table1).Males

firstspawn at age 7 to 8 years, atsizes ofabout 103

cm TL and 4 kg BW. First spawning for females oc-

curs at age 9 to 10years, atabout105 cmTL and6 kg

BW. Spawning individuals in the lower middle

reach are olderthanthose in theuppermiddle

reach. In the lower middle reach, 72.6% of fish were

between age 15 and 28years,whereas in the upper

middle reach, 75.3% of fish were between 13 and 24

years of age(Table 2). Theoldest individual was 45

years. The sexratioalso variedbetweenreaches,

with askewed sex ratio in thelowermiddle reach

(2.0:1,N=251).Between late May andearlyJune,

we examined gonads of 24fishaged 15 to 38 years.

The GSI of these specimens rangedfrom12.7% to

34.7%,averaging23.5 ±5.6%.Fecundity ranged

from 114 000 to 1 292 000 with mean of 385 000. The

number ofeggs pergram of bodyweightranged

from 31.0 to 64.4, with a mean of 44.6. Fecundity was

positivelycorrelatedwithtotal length andage.Ripe

eggsrangedfrom 3.0 to 3.5 mm in diameter.

Kaluga,Huso dauricus

The kaluga is a largefreshwatersturgeonfound

only in theAmurRiver.They tend to besolitary

and non-migratory.Fisheries existthroughout the

mainstream of the middle reach of the Amur River.

Kaluga ranged from 160 to 400 cm TL in the lower

middle reach. Fishbetween 200 and 320 cm TL ac-

Results and discussion

Amur River

The Amur River (also known as the Heilong Jiang)

arisesfrom the confluence of theShilkaand Argun

rivers. From there, it flows nearly 3000 km to its en-

try into the Sea of Okhotsk. Forabout onethird of

its length, theAmurRiver forms the border be-

tweenChina and Russia.Geographersdistinguish

threeportions of theAmurRiverusuallyreferred

to as upper,middle, andlowerAmur. Ourstudies

focus on the sturgeons of the middle Amur, a sec-

tion ofriverabout1005 kmlong,that wesubdivide

into upper andlower middle reaches (Figure l),

with theuppermiddle reach extending between the

towns ofHeihe andLuobei and thelower middle

reach extending from Zhaoxing to Qingdeli. Addi-

tionalinformationabout theAmur and its stur-

geons, particularly populations from the lower

reach andestuary of theAmurRiver, isgiven by

Krykhtin & Svirskii (1997 this volume). Two species

of sturgeons are native to the middle reach of the

AmurRiver.

Amur sturgeon, Acipenser schrenckii

The Amursturgeon ismostlyrestricted to the main

channel of theAmurRiverfrom theuppermiddle

Table 2. Age composition of spawning stock of Acipenser schrenckii in the middle reach of the Amur River.

H-L = upper middle reach from Heihe to Luobei: Z-Q = lower middle reach from Zhaoxing to Qingdeli: Nt = total number of samples;

Nm = number of males; Nf = number of females; and values = individuals.